The present invention relates to a vehicle drive unit capable of quickly supplying hydraulic pressure to a clutch and quickly engaging the clutch when restarting an engine from an engine stopped state established by an idle stop function, for example.
In related art, vehicles have been in practical use with a function of automatically stopping an engine (idle stop function) when a predetermined condition is satisfied during traveling in order to reduce fuel consumption, exhaust gas emission, noise, for example. In such vehicles, for example, the engine is stopped when conditions, such as a condition in which the vehicle speed is zero, a condition in which an accelerator pedal is not depressed, and a condition in which a brake is applied, are all satisfied.
When the engine stops, normally, an oil pump connected to the engine also stops. Thus, for example, oil supplied to a forward drive clutch to be engaged during forward traveling is released from an oil passage, resulting in disengagement of the forward drive clutch.
If a predetermined restart condition is satisfied, such as when the accelerator pedal is depressed by the driver, the stopped engine is restarted, and the oil pump is also restarted. At this time, if the forward drive clutch is not quickly engaged as the engine is restarted, the forward drive clutch engages in a state where the engine is racing, resulting in generating an engagement shock.
Thus, various technologies have been proposed for preventing occurrence of engagement shocks. As one example of such technologies, an accumulator capable of accumulating hydraulic pressure is provided branching from an oil passage that connects a forward drive clutch of an automatic transmission and an oil pump for generating the hydraulic pressure to supply the hydraulic pressure to the forward drive clutch (Japanese Patent Application Publication No. 2000-313252). When restarting the engine, the occurrence of engagement shocks is prevented by supplying the hydraulic pressure accumulated in the accumulator to the forward drive clutch, whereby restartability of the engine is enhanced.